It is lunchtime at the South of Market dojo, and a handful of aikidokas are falling and rolling, thrusting and pinning, creating a chorus of sounds as bare hands and feet slap the thick mat.

In the center is Ragnar Bohlin, who uses his partner's attack to fluidly somersault from standing position to mat to standing position. The practice appears part dance, part combat - punctuated throughout by the sounds of slapping, tumbling and exhaling.

For Bohlin, the Swedish-born chorus director of the San Francisco Symphony who has practiced aikido for 24 years, there is a harmony between his practice and his profession.

"Aikido is about blending with your opponent, it's about control and balance," Bohlin said, wiping sweat from his brow as he took a break at the Suginami Aikikai studio, a half dozen blocks from Davies Hall. "Music and aikido are about harmonizing energies, about finding a perfect blend, pitch, timing and sense of togetherness."

Practicing the Japanese martial art helps Bohlin, 44, a celebrated former choir master in Stockholm whose grandfather was an opera singer and whose mother and father were choir directors, prepare for his work onstage.

"In aikido, a lot of energy goes through your hands, and in music, a lot of energy goes through your hands," said Bohlin, a first-rank black belt. "You need to direct the energy and harmonize that energy. With conducting, I want the chorus to breathe together, phrase together and be together with my movements."

Aikido teaches that instead of meeting force with force, practitioners take their opponents' energy and turn it back. It is about self-defense, and also about protecting the attacker from injury.

"I started aikido while a student at the Conservatory of Music in Stockholm," Bohlin said. "I went to see a Japanese master demonstrate aikido, and was just so impressed." He has come to appreciate the philosophy behind the practice.

"Aikido is comprised of three syllables," Bohlin said. "Ai means together, ki means power or life force, and do is the suffix used for way of enlightenment."

"It's like meditation for me," he said. "It gives you freshness, vitality."

He tries to practice three times a week, but has had months and even years when work, travel and family - he and his wife, a cellist, have two sons - took him away from aikido.

"I always come back to it," he said.

"Aikido is like conducting - and helps me with conducting - because you need to be very focused," Bohlin said, returning to the mat. "You train your awareness. With aikido, you want to be one with your partner. With music, I want to be one with the chorus."

In the Zone

In an occasional series, The Chronicle takes a look at what artists do behind the scenes to harness creativity and stay fit for their performances.